When updating statistics of previous months, the following items cannot be measured and will be set to 0: Webs, Topics, Users, Data Size, Pub Size, Disk Use, Plugins.

Charts are automatically shown at the top if the TWiki:Plugins.ChartPlugin is installed and enabled (it is not) and if there are at least two months of statistics data. ChartPlugin version 2011-04-27 or later is required.

TWikiSiteTools explains how to enable automatic updates of the statistics pages.